For correct operation of a light emitting diode (LED), the electric current supplied has to be adapted to the operating properties of the LED. For this purpose, a driving electronic system is used, which can be constructed in discrete fashion, i.e. consists of individual electrical components. The latter are situated within the housing, usually below the LED chip in the lamp base, which, in the case of lamps operated by power supply current, simultaneously constitutes electrical and mechanical connection to the lampholder.
In possible driving of the LED upon connection to power supply system voltage, a transformer is used, which transforms the AC voltage to an operating voltage suitable for LED circuit arrangements. Furthermore, an AC-DC rectifier is connected downstream of the transformer, wherein both components together fulfill the function of a power supply unit. For the purpose of voltage smoothing, a capacitor is connected in parallel with the LED connected to the power supply unit as a load.
For suitable current and/or voltage limiting, however, there are also a large number of other possible ballasts.
DE 10 200404768 B4 discloses an LED circuit arrangement in which a voltage supply of, for example, 110 or 220 volts AC voltage is provided. A bridge rectifier, the rectifier diodes of which are radiation-emitting LEDs, is used as rectifier of the AC voltage. Two further LEDs are connected to the bridge rectifier as load. Furthermore, the arrangement comprises at least two multi-chip LEDs each containing two LEDs of the bridge rectifier and one LED of the load.
EP 07 117 245.6 discloses an LED module comprising an LED chip fitted directly or indirectly on a plate composed of silicon. The plate projects laterally beyond the area of the LED chip, which comprises an active light-emitting layer and a substrate. At least one electrical component constituting part of the control circuit of the LED chip is integrated in the silicon plate.
U.S. Pat. No. 6,710,376 B2 discloses an optocoupler consisting completely of silicon and comprising two substrate layers separated by a transparent insulator. An LED is fitted on the top side of the lower layer and the top side of the upper layer has a light sensor, wherein the light sensor is configured such that it can detect light emitted by the LED. Furthermore, methods are disclosed as to how circuits can be insulated from the LED or the light sensor, that CMOS and bipolar circuits can be added to both silicon layers in any desired manner.
DE 10 2006 037292 A1 discloses a light source comprising a plurality of LEDs fixed on a substrate, and a sensor for measuring light from the LEDs. Each LED emits light having a different spectrum than the other LEDs. The sensor generates a plurality of signals, wherein each signal is characterized by a sensor value that is proportional to the light intensity emitted by a corresponding one of the LEDs.
U.S. Pat. No. 5,962,906 discloses a possible construction of a diode color sensor, in particular of a CMOS sensor.
The problem that exists, then, is that a constant lighting, for example of rooms or of display windows, under a wide variety of conditions, such as different times of day, is desirable. On account of the different conditions, however, an optimum artificial lighting also has to be individually adaptable thereto. At the same time, it is desirable to utilize existing connection possibilities when using new and more energy-saving technologies, as is possible with retrofit LED modules as an incandescent bulb replacement. However, they have to fulfill predefined standards such as dimensions of the lampholders or properties of the voltage supply.